Can a pool of water be used to reflect heat from light?

Question

I am designing a low impact house. I had planned to use a reflecting pool of water to increase the passive solar gain in the house in winter:

and reflect it away in the summer (note the structure on the left side of the house is a lean to greenhouse which is why the light is shown as traveling through it):

Someone reading my plans suggested that:

Whilst the reflectance pool would undoubtedly contribute to daylighting and would help in the winter months to reduce use of artificial lighting, it is suggested that the water may absorb most of the incoming shortwave energy and release longwave radiation (heat) back to the sky.

Is above statement true?

A StackExchange on whether reflection preserve wavelength suggests that a perfect mirror will preserve wavelength. Reflecting both heat and light. I understand that the surface of the water is not a perfect mirror and that only a proportion of the light/heat would be reflected.

This meteorologist seems to confirm that a low sun will reflect heat:

When the sun is low on the horizon (low sun angle) more radiation will be reflected off water.. A low sun angle has a more difficult time warming water because a great percentage of the solar radiation is reflected away.

Would the reflecting pool illustrated contribute heat to the house in the winter? Would the sunlight reflected by it contain longwave radiation (heat)?

Answer 1

In short, yes. According to the Fresnel equations, reflection is higher at low angles. https://en.wikipedia.org/wiki/Fresnel_equations

It is true that water absorbs shortwave radiation but that's only if the radiation is passing through the water. Ultimately, Maxwell's equations have to be satisfied at the interface, which causes the grazing reflection that you have likely noticed in your everyday experiences with water surfaces.

Comparing the water scenario to having a patch of ground instead, the water is likely better for heating the house. But since it is most effective at low angles, it is unclear whether the Sun can be low enough to cause significant heating. It is also unclear whether much power will be transmitted, because the effective surface area of the pool is reduced: $A_{\rm eff} = A_{\rm pool} \sin{\theta}$ when the Sun's angle is low. Not clear whether the higher-impact inclusion of the pool ends up balancing the lower-impact heating.